Recognisability Equals Definability for Finitely Representable Matroids of Bounded Path-Width

Let ${\mathbb{F}}$ be a finite field. We prove that there is an MSO-transduction which, given an ${\mathbb{F}}$-representable matroid of path-width k, produces a branch-decomposition of width at most f(k), for some function f. As a corollary, any recognizable property of ${\mathbb{F}}$-representable matroids with bounded path-width is definable in MSO logic, and therefore recognizability is equivalent to MSO-definability on classes of ${\mathbb{F}}$-representable matroids of bounded path-width. This generalizes the result of Bojańczyk, Grohe and Pilipczuk [Logical Methods in Computer Science 17(1), 2021] which asserts the equivalence of the two notions on graphs of bounded linear clique-width.